Positioner for maintaining an object in a substantially weightless condition

ABSTRACT

A system for positioning an electronic test head of a test system with respect to an electronic device handler. A housing is provided having a vertical shaft. A positioner assembly moves vertically with respect to the shaft and provides substantial movement in the horizontal plane with six degrees of freedom. The positioner assembly includes a section for attaching the test head. A counterbalancing assembly is coupled to the positioner assembly and has a counterweight to provide a substantially weightless condition to the positioner assembly with the test head attached.

This application is a continuation of application Ser. No. 411,311,filed Aug. 25, 1982, now U.S. Pat. No. 4,527,942.

BACKGROUND OF THE INVENTION

A. Field of the Invention

This invention relates to the field of art of electronic test headpositioners.

B. Background Art

In the automatic testing of integrated circuits (IC) and otherelectronic devices, special device handlers have been used which placethe device to be tested in position. The electronic testing itself isprovided by a large and expensive automatic testing system whichincludes a test head which has been required to connect to and dock withthe device handler. In such testing systems, the test head has beenusually very heavy in the order of 100 to 150 pounds. The reason forthis heaviness is that the test head uses high speed electronic timingsignals so that the electronic circuits must be located as close aspossible to the device under test. Accordingly, the test head has beendensely packaged with electronic circuits in order to achieve the highspeed testing of the sophisticated devices.

The prior art has left much to be desired in providing a manipulator orpositioner to easily move the heavy test head accurately into positionwith respect to the device handler mechanism. In some prior positionersthe test head has been positioned by means of lead screws and rotatingand sliding mechanisms each movable one at a time. These prior systemsleft much to be desired in that they did not provide all of the degreesof freedom necessary for easy and accurate docking with the handler. Theuser has had to move the heavy device handler or the heavy positioneritself in order to provide alignment. Other prior art manipulatingsystems have used motors to drive rhe lead screws in the up/downdirection. Such a motor driven lead screw or even a hand driven oneprovides the possibility of damaging either the test head socketconnections or the connections which are on the device handler due tooverstressing.

Another disadvantage of the prior art systems is that they are large andtake up a considerable amount of floor space which is at a premium intest facilities. A further difficulty of large prior systems hasinvolved the cable which connects the test system to the test head whichis usually short, cumbersome and fragile. Accordingly as a result oftheir size and construction, prior systems could not be movedsufficiently close to the test system.

Accordingly, an object of the present invention is an electronic testhead positioner that has six degrees of freedom and provides asubstantially weightless condition to the test head which may bemanipulated by hand for easy and accurate docking and undocking of thetest head with the device handler.

Another object of the invention is an electronic test head positionerformed by a column rising vertically from a base which takes little roomon the floor with respect to the test system.

SUMMARY OF THE INVENTION

A system for positioning an electronic test head with respect to anelectronic device handler which comprises a housing including shaftmeans. A positioner assembly has vertical movement along the shaft meansand provides substantial movement in the horizontal plane with sixdegrees of freedom. The positioner assembly includes means for attachingthe test head. Counterbalancing means is coupled to the positioner andincludes a counterweight to provide a substantially weightless conditionto the positioner assembly with the test head attached.

BREIF DESCRIPTION OF THE DRAWINGS

FIGS. 1-3 are perspective view of a test head positioner system inaccordance with the present invention;

FIG. 4 is a sectional view of FIG. 3;

FIG. 5 is a diagrammatic view of the system of FIGS. 1-3 showing thedocking of a test head with a mechanism plate of a handler;

FIG. 6 diagrammatically shows the six degrees of freedom of the systemof FIGS. 1-3; and

FIGS. 7A-C show further embodiments of the invention with respect tosecuring the positioner system alongside the test system.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 5, there is shown a test head positioner system 10in accordance with the invention. As shown, positioner system 10 carriesa test head 11 for a test system for docking with a mechanism plate 17of an integrated circuit handler 15. It will be understood that otherelectronic devices may be handled by device handler such as transistors,chips or dies, etc. In operation, positioner system 10 is moved manuallyin a substantially weightless condition to manipulate the heavy testhead 11 accurately and precisely and dock it into the mechanism plate17. In docking, location pins 11b are inserted into correspondingopenings in plate 17 and test connector 11a enters and mates with thedevice 15a to be tested. As will later be described in detail, theposition of test head 11 may be accurately manipulated in asubstantially weightless condition to another position with six degreesof freedom to dock with other mechanism plates in any position. Forexample, mechanism plates for probers or handlers may be anywhere from ahorizontal plane to a vertical plane.

The details of positioner system 10 are shown in FIGS. 1-3 in whichthere is provided a H-shaped beam forming a vertical housing or column12. Column 12 has opposing walls 12a,b with a flange or webb 12cconnecting the two walls together. Column 12 is supported at its bottomby a base assembly 20 having a base plate 22 and outwardly extendinglegs 24a-e which are bolted to the bottom of plate 22, for example.Column 12 is secured to plate 22 by bolts 22a for example. The rear ofcolumn 12 is closed by a U-shaped door 14 which is hinged to the outersurface of wall 12b by way of hinges 16.

Test head 11, FIG. 5, is supported and manipulated in its docking by apositioner arm assembly 30 which is adapted to move vertically on a mainshaft 50. Assembly 30 comprises a main arm assembly 32, a forearmassembly 34, a wrist joint assembly 36, a cradle assembly 38 and testhead adapter plates 40a,b. Main shaft 50 is secured in place on thefront section of column 12 by opposing pillow blocks 52,53.

Positioner arm assembly 30 is adapted to ride vertically on main shaft50 by a counter weight assembly 60 having a weight carriage 62 whichmoves vertically in either direction within the rear section of column12. Carriage 62 has vertically extending shafts 65a,b secured theretoand weights 62a-c are removably received and carried by the carriage.Weights 62a-c are added to exactly counterbalance the weight of assembly30 together with the test head so that the test head and assembly 30 aresubstantially weightless.

The upper ends of carriage shafts 65a,b are formed into eye bolts 65a,bto securely receive flexible cables 68a,b respectively. In anotherembodiment (not shown) shafts 65a,b may be threaded to receive threadedmembers swaged to receive the cable ends. Cables 68a,b are receivedwithin grooves of pulleys 72a,b respectively of pulley assembly 70.Assembly 70 has a shaft 74 which permits the rotation of pulleys 72a,band is received at an upper end section of column 12 in openings inwalls 12a,b respectively. Cables 68a,b then extend downwardly along theinner surface of walls 12a,b and are securely fastened to a lift block80 which is positioned under main arm assembly 32 and has an opening forreceiving shaft 50. Block 80 slides along web 12c and is thus preventedfrom rotating around shaft 50. A thrust bearing 89 is provided betweenblock 80 and a lower bearing block 87 of arm assembly 32 to permitassembly 32 to rotate to a limited extent about shaft 50 while block 80is unable to so rotate.

Referring now to FIG. 3, there is shown the details of positioner armassembly 30. Specifically, main arm assembly 32 includes an upperbearing block 86 and a lower bearing block 87. Bearing blocks 86, 87have respective lower extending and upper extending sections 86a, 87aand as shown engage an I beam 90. Specifically, a front wall 90a of Ibeam 90 is secured by screws to front faces of blocks 86, 87 while arear section 90b of I beam 90 is secured by screws to sections 86a, 87arespectively. ln this way a unitary main arm assembly 32 is formed whichis adapted to have vertical movement and rotational movement (about avertical axis) on a vertical shaft 50 by means of combination bearingset 88 for block 86 and combination bearing set 89 for bearing 87.Combination bearing sets are well known in the art and are made forexample by Thompson Industries. The vertical and rotational movements ofassembly 32 may be temporarily locked in any position by means of a mainarm assembly lock 55 formed in block 91 and this lock will later bedescribed in detail.

Secured to front face 90a of I beam 90 are a pair of pillow blocks 95,96 of forearm assembly 34. A vertical shaft 98 extends through pillowblocks 95, 96 and is secured in place by a screw 99a. Forearm assembly34 further includes a forearm 100 having a rear section 101 which isbolted to forearm 100 by means of bolts. Shaft 98 extends throughvertical opening 107 in section 101 with needle bearings 102, 103 ateither end of section 101 and a thrust bearing 105 between the lowerportion of section 101 and the upper face of pillow block 96. Forearmassembly 34 may be temporarily fixed in its rotational position about avertical axis by means of a forearm lock assembly 106.

Forearm 100 has a front "C" shaped section which rotatively receives anattachment member 120 of wrist joint assembly 36. Member 120 rotateswith respect to forearm 100 by way of a vertical shaft 122 which extendsthrough a vertical opening in forearm 100, through member 120 and theninto a lower opening in forearm 100. Needle bearings 124, 125 areprovided for the rotation of shaft 122 in forearm 100 and a thrustbearing 128 is provided between the lower surface of member 120 and theupper surface of forearm 100. Shaft 122 is rigidly secured within member120. Member 120 may be temporarily prevented from rotation by means of awrist joint lock assembly 110 which is formed within a block 112 securedto the upper surface of forearm 100.

Cradle assembly 38 is formed by three walls 130-132 welded together toform a U-shaped holder for the test head. Assembly 38 is rotatable withrespect to member 120 by means of a horizontal bolt 133 which extendsthrough wall 130 and is threadedly received in member 120. For bearingsurfaces, bolt 133 extends into a stainless steel bushing and betweenthe back surface of wall 130 and member 120 there is provided astainless steel plate (not shown). Bolt 133 and the bearing surfaces areeffective to allow the rotation of assembly 38 about a horizontal axisand assembly 38 may be secured in position by tightening of the bolt.

Walls or arms 131, 132 are adapted to receive test head adapter plates40a,b and to allow these plates to rotate with respect to the walls andthen to be rigidly fixed in position. Since the structure of both of theplates 40a,b are the same only one of them need be described in detail.Accordingly, arm 131 has within an end section a circular groove 135 andan opening 136 for receiving a shoulder screw 137 which is threadedlyengaged in plate 40a. A lock knob 140 is threaded into plate 40a andmoves about circular groove 135 in conventional manner. In this way, bytightening lock knob 140, plate 40a is rigidly secured with respect toarm 131.

It will now be understood that test head positioner system 10simultaneously positions in six degrees of freedom, X, Y, Z, θ_(X),θ_(Y), θ_(Z). As shown in FIG. 6, it is important for the proper dockingof test head 11 that the test connector 11a have that six degrees offreedom so that it can accurately and effortlessly be positioned withrespect to the device to be tested 15a, for example. If the Y directionwere considered to be the vertical or up/down direction then themovement of assembly 32 vertically with respect to shaft 50 provides theY direction of freedom. θ_(Y) freedom, which is the rotation about the Yaxis is then provided by simultaneous rotation of all of the jointsabout vertical axes 50, 98 and 122.

If the X direction were considered to be the left to right direction,then that freedom is provided by pivots 50, 98 and 122 in the samemanner as θ_(Y). The θ_(X) freedom is provided by shoulder screw pivot137. With respect to Z movement which may be considered to be the in andout movement, such freedom is provided by pivot shafts 50, 98 and 122 inthe same way as θ_(Y), θ_(Z) is then provided by the freedom about screwpivot 133.

Referring now to FIG. 4, there is shown a main arm assembly lock 55which comprises the conventional wedge lock system. Specifically, twowedges 150 and 152 are provided on either side of shaft 50 and arethreadedly engaged by threads 154 of a lock handle 153. By turning lockhandle 153 clockwise, wedge members 150, 152 are brought together andapply pressure onto shaft 50 and this way prevent rotation of block 91about shaft 50 and also prevent a vertical movement of block 91 and theentire assembly 30. Similar lock assemblies are provided for forearmlock assembly 106 and wrist joint lock assembly 110 which have turningarms 106a and 110a respectively.

It will now be understood that test head positioner system 10 provides acounterbalancing system which produces a weightless condition to thepositioner arm assembly 30. In this manner, the test head 11 may bemoved in this weightless condition substantially extensible in thehorizontal plane and with six degrees of motion to provide the ease indocking.

Those skilled in the art will understand that various changes may bemade in further embodiments of the invention without departing from thespirit or scope of the invention.

Referring to FIG. 7A there is shown base plate 22 which is directlybolted onto the floor immediately next to test cabinet 11c of the testsystem. For purposes of simplicity the elements within column 12 havenot been shown. In still another embodiment shown in FIG. 7B a base 22chas attached to its lower surface along one side a rigid horizontal baror leg 160. Mounting bolts 162 are used to secure bar 160 to the bottomof cabinet 11c. A leveling pad 164 remote from bar 160 on base 22aprovides leveling of the base. A further bar or strut 165 is secured bybolts to the top of cabinet 11c and to wall 12a of column 12. In thismanner, column 12 is rigidly secured close to test cabinet 11c so thatsystem 10 is as close as possible to the test system. In still a furtherembodiment as shown in FIG. 7C, a base 22d has connected to its lowersurface perpendicular legs 170, 171 connected to adjacent sidewalls oftest cabinet 11c. A leveling pad 174 may be provided for the leveling ofthe base. Instead of being bolted to cabinet 11c, bars 170, 171 may beextended (not shown) and coupled to two additional bars holding theremaining two sides of the cabinet. Thus, the four bars may be bolted toeach other to rigidly engage cabinet 11c.

It will also be understood that forearm assembly 34 may be effectivelyturned 180° while maintaining all the other elements in their originalpositions. In this manner, rear section 101 extends to the left ascompared to the right as shown in FIG. 3.

What is claimed is:
 1. A system for maintaining an object in asubstantially weightless condition without the effect of gravitycomprisingsupport means, positioner means coupled to the support meansand having vertical movement with respect to the support means andmovement in the horizontal plane, the positioner means including meansfor attaching the object, counterbalancing means coupled to thepositioner means to provide substantially weightless condition to thepositioner means with the object attached, and the positioner means andthe support means including at least three parallel continuouslyvertical axes so that as the positioner means is extended in thehorizontal plane, the three vertical axes themselves support the weightof the positioner means with the object and two of the three verticalaxes being simultaneously free to rotate about their respective axes asthe positioner means is manually rotated about said two vertical axeswithout the effect of gravity, at least one of said two vertical axesbeing free of vertical movement with respect to the positioner means. 2.The system of claim 1 in which the other of said two vertical axes isfree of vertical movement with respect to the positioner means.
 3. Thesystem of claim 2 in which the support means includes a continuouslyvertical shaft forming a third of the three vertical axes for providingvertical movement of the positioner means along said shaft.
 4. Thesystem of claim 2 in which the positioner means includes means forproviding rotation about said two vertical axes and free of axes betweensaid two vertical axes.
 5. The system of claim 3 in which saidpositioner means is free of axes between said two vertical axes andbetween said two vertical axes and said third vertical axis.